IMS: Reset mHold flag once call is merged

When Conference call is on HOLD and merged, mHold flag is required
to be reset explicitly as Telephony does not send RESUME request
in this scenario.

Bug: 18625579
Change-Id: Icb0b2b52d7dfe64c456b4e7c1b2e7458640ee1da
diff --git a/src/java/com/android/ims/ImsCall.java b/src/java/com/android/ims/ImsCall.java
index 4bcae1a..3873af8 100644
--- a/src/java/com/android/ims/ImsCall.java
+++ b/src/java/com/android/ims/ImsCall.java
@@ -1928,6 +1928,7 @@
                 listener = mListener;
                 mCallProfile = profile;
                 mUpdateRequest = UPDATE_NONE;
+                mHold = false;
             }
 
             if (listener != null) {